Many modern communications networks utilize packet switched (PS) signaling to transmit and receive data between devices, such as between mobile terminals and various network devices. In order to utilize a PS signaling scheme, a PS signaling connection can be obtained between a mobile terminal and the network. In order to obtain a PS signaling connection, a session establishment procedure generally initially takes place between the mobile terminal and the network. For example, a session establishment procedure can be a network initiated paging procedure or a mobile terminal initiated service request procedure. Each session establishment procedure can consume network resources and, as such, avoiding unnecessary session establishment procedures is desirable.
By way of example, the technical specifications of the Third Generation Partnership Project (3GPP) and, in particular, 3GPP TS 24.008, REL 6 and REL 7A (hereinafter the 3GPP specification) describe an approach for either maintaining or releasing a PS connection following general packet radio service (GPRS) attach and routing area update procedures. In this regard, third generation (3G) networks use a follow on proceed bit in the attach result and update result information to indicate whether the PS connection should be maintained or released. If the follow on proceed mode is selected, such as in instances in which PS signaling is anticipated, the PS signaling connection will remain open following the GPRS attach and routing area update procedures, thereby avoiding the network resource consumption otherwise required to close the connection that was established for the GPRS attach and routing area update procedure only to have to reestablish a connection to support the impending PS signaling. On the other hand, if the follow on proceed bit is set in a no follow on proceed mode, such as in instances in which PS signaling is not anticipated, the connection between the mobile terminal and the network will be automatically released. In this mode, a timer, referred to as T3340 in the 3GPP specification, is set and the PS signaling connection only remains open until the timer expires. When the timer expires, for example after ten seconds, the mobile terminal notifies the network's radio resource controller (RRC), and the RRC releases the PS signaling connection.
As noted above, the no follow on proceed mode is generally selected in instances in which there is no known need for further PS signaling. Since the PS signaling connection remains open for a period of time, such as the duration of a timer, even when the no follow on proceed mode is selected, PS signaling can be exchanged between the mobile terminal and the network during this period of time, that is, while the timer is running. However, when the timer expires, any ongoing or impending PS signaling is interrupted by the mobile terminal's initiation of a release of the connection. As a result, a new connection must be established to support or complete the PS signaling. The establishment of a new connection can lead to unnecessary utilization of network resources and, in some instances, latency. In a 3G network, for example, this situation may arise because, even though signaling by the mobile terminal may be prohibited while timer T3440 is active, the network may still initiate communications with the mobile terminal. For example, a session management procedure could be initiated by the network which would be ongoing at the time that the timer expires and the connection is closed.
FIG. 1 depicts a signaling sequence in which the no follow on proceed mode is selected by the network since no data or session management/GPRS mobility management protocol data units (SM/GMM PDUs) need to be sent to the mobile terminal at the time the network is accepting the routing area update request, thereby causing subsequent PS signaling to be interrupted. The signaling sequence depicts communications between a mobile terminal, also known as user equipment, 100 and a network 105. Prior to event 125, a session has been established and a PS signaling connection has been opened between the user equipment 100 and the network 105. At event 125, a routing area update request is sent from the user equipment 100 to the network 105. Upon receipt of this request, the network 105 transmits a routing area update accept at 130. Additionally, at 130, the network sets the follow on proceed bit 115 to reflect the no follow on proceed mode. Accordingly, timer 110 is triggered at the user equipment 100. Before timer 110 expires at 145, an initial Internet Protocol (IP) data packet, which is part of a larger group of IP data packets, is sent to the user equipment 100 at 135. Timer 110 then expires at 145, before the entire group of IP data packets is sent or received by the user equipment 100. Also at 145, the user equipment 100 interrupts the reception and transmission of the IP data packets and initiates a release of the PS signaling connection. Accordingly, the RRC releases the PS signaling connection at 150. Since some of the group of IP data packets have yet to be sent or received by user equipment 100, a new session establishment must occur at 155. Subsequently, the remaining packets of the group of IP data can then be sent or received at 160, 165, and 170.
Thus, the signaling sequence of FIG. 1 depicts a scenario where a PS signaling connection is released, and then must be reestablished even though additional PS signaling commenced prior to the release, since the initial selection of the no follow on proceed mode initiates the automatic release of the connection following the expiration of the timer. In this scenario, the release and reestablishment procedures unnecessarily utilize resources of both the user equipment and the network, and may impair the end user's experience, or quality of service, due to potentially increased latency in the data transfer.
Accordingly, it may be advantageous to provide an improved mechanism for avoiding unnecessary release and reestablishment procedures by maintaining an open PS signaling connection in certain circumstances including, for example, when additional PS signals are transmitted following the selection of a no follow on proceed mode.